This invention relates to polyurethane foam. This invention particularly relates to polyurethane foam useful with and for preparing carpet underlay and attached cushion carpets.
It is known in the art of preparing textile articles, such as carpets, to use polyurethanes as backings in various forms. For example, U.S. Pat. No. 4,296,159 to Jenkines, et al., discloses preparing a tufted or woven article having a unitary backing prepared by applying a polyurethane forming composition to the underside of the tufted or woven article. A different form of polyurethane backing is disclosed in U.S. Pat. No. 5,102,714 to Mobley, et al. wherein the polyurethane backing is a tacky adhesive. It is also known to use polyurethane foam as a cushioning textile backing, as in, for example, U.S. Pat. No. 4,853,280.
There are several properties of polyurethane foams which are important for determining their usefulness in carpet applications. These properties include but are not limited to resiliency, dimensional stability, and cost. Cost is a very important property because of the highly competitive nature of the carpet industry. However, if a carpet does not properly install or rolls up after installation, or if that carpet is unpleasant to walk on due to poor resilience or dimensional stability of the attached or separate polyurethane pads, the carpet is not desirable to purchasers. Thus, there is a substantial body of art relating to preparing polyurethane foams useful for carpet applications wherein the polyurethane foams have good resiliency and dimensional stability and can be prepared at low cost.
One means of preparing polyurethane foams at a lower cost is to reduce the density of the polyurethane foam. Polyurethane foams are generally prepared by admixing an A component, a polyisocyanate, with a B component, an active hydrogen containing material, wherein a gas is either mechanically Introduced or produced chemically forming bubbles which form a cell-like structure in the cured polyurethane. The process of introducing the bubbles is known as blowing the formulation. The greater the amount of gas introduced into a polyurethane formulation, the lower the density of the resultant foam produced therewith. But with polyurethane foams generally and with polyurethane foams used in carpet applications in particular, reducing foam density can also decrease or reduce the properties of the polyurethane foam which can make it a desirable material for use in carpet applications. Therefore, it would be desirable in the art of preparing polyurethane foam for carpet applications to prepare such foam with a substantially lower density than conventional polyurethane carpet foams and yet retain the desirable properties of conventional polyurethane foams.
In one aspect, the present invention is, in a process for preparing a polyurethane foam pad for use as either an attached carpet cushion or a detached carpet underlay wherein a polyurethane formulation, including a polyisocyanate, is admixed using a frother, the improvement comprising including in the polyurethane formulation from about 0.5 to about 3 parts water per hundred parts of polyol, from about 0.01 to about 3.5 parts urethane catalyst per hundred parts of polyol, and from 1 to 2 parts surfactant per hundred parts of polyol under reaction conditions such the foam is both frothed and chemically blown.
In another aspect the present invention is a polyurethane foam prepared by a process wherein a polyurethane foam formulation is both frothed and chemically blown.
In still another aspect, the present invention is a polyurethane formulation useful for preparing polyurethane foams comprising a polyisocyanate, a polyol, from about 0.5 to about 3 parts water per hundred parts of polyol, from about 0.01 to about 3.5 parts urethane catalyst per hundred parts of polyol, and from 1 to 2 parts surfactant per hundred parts of polyol.